...

type
  pstr   = ^tstr;
    tstr = record
    str1  : string; //ID1
    str2  : string; //Template
    str3  : string; //Script
    str4  : string; //Description
  end;

var
  FolderID  : pstr;

procedure TfrmReport.FillTree;
var
  TreeNode: TTreeNode;
  procedure FillTreeNode(TreeNode: TTreeNode);
  var
    I: Integer;
    Node: TTreeNode;
  begin
    FolderID := TreeNode.Data;
    DS_CHILD.DataSet.Filtered := FALSE;
    DS_CHILD.DataSet.Filter   := 'rep_ID2=' + #39 + FolderID.str1 + #39;
    DS_CHILD.DataSet.Filtered := True;

    DS_CHILD.DataSet.First;
    for I := 0 to DS_CHILD.DataSet.RecordCount - 1 do begin
      Node := TreeView.Items.AddChild(TreeNode, DS_CHILD.DataSet.FindField('rep_title').AsString);
      New(FolderID);
      FolderID.str1 := DS_CHILD.DataSet.FindField('rep_ID1').AsString;
      Node.Data := FolderID;
      Node.ImageIndex := 0;
      Node.SelectedIndex := 1;
      DS_CHILD.DataSet.Next;
    end; // for I := 0 to DS_CHILD.DataSet.RecordCount
    for I := 0 to TreeNode.Count - 1 do begin
      FillTreeNode(TreeNode.Item[I]);
    end; // for I := 0 to TreeNode.Count
  end;
begin
  try
    LockWindowUpdate(self.Handle);
    TreeView.Items.BeginUpdate;
    TreeView.Items.Clear;

    while not DS_ROOT.DataSet.Eof do begin
      with TreeView.Items.Add(nil, DS_ROOT.DataSet.FieldByName('rep_title').AsString) do begin
        New(FolderID);
        FolderID.str1 := DS_ROOT.DataSet.FieldByName('rep_ID1').AsString;
        Data          := FolderID;
        ImageIndex    := 0;
        SelectedIndex := 1;
      end; // with TreeView.Items.Add
      TreeView.Canvas.Font.Style := [fsBold];
      FillTreeNode(TreeView.Items[0]);
      DS_ROOT.DataSet.Next;
    end; // while not DS_ROOT.DataSet.Eof

    TreeView.FullExpand;
    TreeView.Items.EndUpdate;
    if DS_ROOT.DataSet.RecordCount > 0 then TreeView.Items[0].Selected := True;
  finally
    LockWindowUpdate(0);
  end;
end;